About the kids and their upbringing....
We really do not know how these kids got this good. I have to believe that these kids have some pretty amazing talent compared to the average person. The girl is probably just extremely talented, while the boy seems like a prodigy.
I have been lucky enough to teach a handful of students like this in the last 40 years. Out of 4400+ students, I have seen possibly 6 students that were as talented (and I could probably name them all). These were folks who had the ability to be shown something just once and were able to play it either immediately of after one try. And I am not talking simple chord forms here, I am talking about intricate melodies or complex music theory concepts. Zeb's ability to improvise at the level he does on the tune Sally Goodin is really unbelievable for someone so young. I believe he is essentially at a genius talent level for music.
Don't get me wrong, even with prodigy level talent, these kids still put a ridiculous number of hours in on their instruments and deserve serious kudos. But I kind of doubt that they were forced to play music, as they seem to enjoy it so much. And I think they are already at a level that has them cemented as well paid performers for the rest of their lives if they so choose; so their youth was certainly not wasted. I believe Zeb is in the running for IBMA guitarist of the year and the band is in the running for IBMA new band of the year.
Finally, these kids are well beyond good. If they spend a little more time on their singing, I have no doubt we will be following them as top performers/entertainers for the rest of their lives.